1996A&A...311..189S

An extensive study of radial velocity data of more than 250 Cepheid variables taken from the literature has resulted in revealing spectroscopic-binary nature of 22 classical Cepheids: SS CMa, VZ CMa, VY Car, EY Car, FR Car, SY Cas, CG Cas, VW Cen, OO Cen, SU Cru, VX Cru, TZ Mon, XX Mon, RT Mus, CR Ori, LS Pup, YZ Sgr, AV Sgr, RU Sct, DP Vel, U Vul and SV Vul. The amplitude of the orbital effect superimposed on the pulsational radial velocity variation exceeds 10km/s in eight cases and there are obvious changes in the γ-velocity for the other Cepheids, as well. Additional photometric evidence of duplicity is available for 8 variables in this sample. Each star discussed in this paper is recommended for thorough study in order to determine the orbital elements and physical parameters of companion star(s). The large number of newly found spectroscopic binaries confirms the recent result (Szabados) that incidence of binaries among classical Cepheids is higher than usually believed.